Ultrafiltration of vinyl resin latices and reuse of permeate in emulsion polymerization

摘要

There is disclosed a process of preparing vinyl dispersion resins by conducting the polymerization reaction of the vinyl monomer or monomers in an aqueous medium in the presence of a polymerization initiator or catalyst and an emulsifier or emulsifier system to form a vinyl resin latex, which is then subjected to an ultrafiltration step by forcing the same through a semipermeable membrane leaving behind the polymer particles and reusing the permeate, which contains dissolved monomer(s) and emulsifier, in the further production of vinyl resin latices. Unexpectedly, further use of the permeate substantially reduces polymer buildup in the reactor and since the ultrafiltration step increases the polymer particle concentration in the latex, considerable heat energy is saved in the spray-drying step.